When to plant watermelons in Fort Collins: 7 June – 12 July

In Fort Collins, watermelon: sow for seedlings from 19 April to 14 June; plant into a greenhouse from 17 May to 12 July; plant out into open ground from 7 June to 12 July. For plants and seeds, the places nearby include Bath Garden Center and Nursery (garden centre, 3 km) and Fort Collins Nursery (garden centre, 4 km); addresses and opening hours are below.

Watermelon in Fort Collins: soil, season and weather

In Fort Collins the soil, not frost, sets the date: the last frost is over around 25 April, but the top 7 cm of soil reaches 18 °C — the minimum on the watermelon card — only around 7 June, 43 days later.

Last spring frost	25 April
Top 7 cm of soil at 18 °C	7 June, 43 days after the last frost
Into an unheated greenhouse	17 May – 12 July; May outside: 6.4 °C at night, 21.1 °C by day; card 18–35 °C
First autumn frost	21 October, 136 days after the start
Days in the bed to the first harvest (card)	59
First harvest, if planted in this window	5 August – 9 September
Days left for picking	77
Daylight	14:15 on 10 May, 14:58 on 7 June
Watering outdoors when fruiting (card)	every 5 days; the driest month, October, has 4 rainy days

The same dates in Fort Collins hold for Cucumber, Bell Pepper, Eggplant, Zucchini and Pumpkin.

Watermelon in Fort Collins: care after planting

Planted on 7 June: in the first weeks water every 5 days.

Feeding, by the card’s schedule from that day:

7 June — feed: balanced (NPK)

Pests and diseases of watermelon to watch for:

Dates count from the first planting day of the window above; a later planting moves them by as many days.

Weather in Fort Collins during the watermelon season

No month of the season averages above the watermelon card's 18–35 °C by day; the warmest, July, averages 31.6 °C. Nights average below 18 °C in every month of the season, from 3.8 °C to 16.2 °C.

Month	Day, °C	Night, °C	Rain, mm	Rainy days	Daylight on the 15th
June	28.4	12.7	40	8	15:03
July	31.6	16.2	37	7	14:48
August	30.5	15.2	34	7	13:49
September	27.7	11.2	22	4	12:30
October	18.8	3.8	20	4	11:11

ERA5 2016–2025, Open-Meteo

Watermelon in nearby cities

Around Fort Collins, Pueblo is 35 days earlier and Cheyenne 1 day later.

City	Distance	Date	Difference
Cheyenne	69 km	8 June – 4 July	1 day later
Denver	90 km	28 May – 6 July	10 days earlier
Colorado Springs	192 km	6 June – 6 July	1 day earlier
Pueblo	258 km	3 May – 19 July	35 days earlier
Grand Junction	340 km	6 May – 18 July	32 days earlier
Rapid City	420 km	6 June – 3 July	1 day earlier

Where to buy watermelon plants and seeds near Fort Collins

Buy plants ready to set out from 7 June to 12 July (from 17 May to 12 July for an unheated greenhouse); seed for raising your own is sown from 19 April to 14 June. Within 15 km of Fort Collins OpenStreetMap lists 10 garden centres, 4 farm-supply shops, 2 plant nurseries, 3 markets and 6 farm shops (collected 28 October 2026).

Harmony Gardens — plant nursery
12 km
Bath Garden Center and Nursery — garden centre
East Prospect Road 2000, 80525 Fort Collins · Mon–Fri 08:00–19:00; Sat 08:00–18:00; Sun 09:00–17:00 · 3 km · bathgardencenter.com
Fort Collins Nursery — garden centre
East Mulberry Street 2121, 80524 Fort Collins · Mon–Sat 09:00–17:00; Sun 10:00–17:00 · 4 km · fortcollinsnursery.com
Donath Lake Greenhouses — garden centre
South Lemay Avenue 8420, 80525 Fort Collins · Apr–Jun 09:00–17:00 · 9 km · donathlakegreenhouses.com

Each window starts on the Greenly calendar date and ends on the last day that still leaves the crop’s days to harvest (from its card) before the average first autumn frost, plus six weeks of picking for crops harvested over weeks (tomatoes, peppers, aubergines, cucumbers, courgettes, pumpkins, watermelons, beans) — our rule; earlier in the window is safer.

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